Structural investigation of two viral proteins involved in DNA-packaging

Viral DNA-packaging motors are molecular machines that enable viruses to replicate by providing the means of storing the viral genome into empty procapsids. In double stranded DNA bacteriophages the molecular motor is comprised by three elements: the portal protein and the small and large terminases. The portal protein nucleates polymerisation of the capsid and scaffold proteins, initiating procapsid assembly, besides allowing passage of DNA. The small terminase recognises the viral genome and presents it to the large terminase which possesses both nuclease activity to cleave concatemeric DNA at the initiation of the packaging, and ATPase activity to drive translocation. Although currently several X-ray structures for the different components of the motor from different bacteriophages are available fundamental questions regarding the DNA recognition mechanism, stoichiometry and orientation of the motor components in vivo and the mechanism of ATP-driven DNA-translocation remain. This project focused on elucidating the X-ray crystal structures of (i) the major capsid protein, from Bacillus subtilis bacteriophage SPP1 and (ii) the small terminase protein from Thermus thermophilus bacteriophage G20C. Several constructs of the SPP1 capsid protein, including truncations at the N- and C-termini, single and double mutants and engineered proteins were generated in order to produce a protein suitable for crystallisation. Mutant uG13P;T104Y;A261W was the only construct that produced native and Se-Met crystals. The X-ray structure of the SPP1 capsid protein was determined at 3.0 Å resolution by single wavelength anomalous diffraction. The structure exhibited the HK97-fold consisting of the axial and peripheral domains and the extended E-loop. The X-ray structure of the small terminase from phage G20C was solved at 2.5 Å resolution by single wavelength anomalous diffraction. The structure consisted of circular nine-mers where the N- terminal domains of each subunit reside at the periphery of the assembly and the C-terminal oligomerisation domains form a central channel. The conserved structural features between small terminases suggest that the DNA-recognition mechanism might be conserved. DNA-binding experiments demonstrated that the G20C small terminase binds to viral and non-viral DNA with both the N- and C- terminal domains playing an important role. The structural information generated from these two elements of SPP1 and G20C bacteriophages provides insight into two different aspects of the assembly process: (i) how the capsid protein’s conformational plasticity may assist the assembly and (ii) DNA-recognition during virus particle construction. This information is critical for understanding similar processes in other viruses, in particular, in the evolutionarily related herpes viruses

Cryo-EM structure and in vitro DNA packaging of a thermophilic virus with supersized T=7 capsids

Double-stranded DNA viruses, including bacteriophages and herpesviruses, package their genomes into preformed capsids, using ATP-driven motors. Seeking to advance structural and mechanistic understanding, we established in vitro packaging for a thermostable bacteriophage, P23-45 of Thermus thermophilus Both the unexpanded procapsid and the expanded mature capsid can package DNA in the presence of packaging ATPase over the 20 °C to 70 °C temperature range, with optimum activity at 50 °C to 65 °C. Cryo-EM reconstructions for the mature and immature capsids at 3.7-Å and 4.4-Å resolution, respectively, reveal conformational changes during capsid expansion. Capsomer interactions in the expanded capsid are reinforced by formation of intersubunit β-sheets with N-terminal segments of auxiliary protein trimers. Unexpectedly, the capsid has T=7 quasi-symmetry, despite the P23-45 genome being twice as large as those of known T=7 phages, in which the DNA is compacted to near-crystalline density. Our data explain this anomaly, showing how the canonical HK97 fold has adapted to double the volume of the capsid, while maintaining its structural integrity. Reconstructions of the procapsid and the expanded capsid defined the structure of the single vertex containing the portal protein. Together with a 1.95-Å resolution crystal structure of the portal protein and DNA packaging assays, these reconstructions indicate that capsid expansion affects the conformation of the portal protein, while still allowing DNA to be packaged. These observations suggest a mechanism by which structural events inside the capsid can be communicated to the outside

La sociología de la salud y los paradigmas de investigación

El presente libro se deriva del trabajo colegiado de la investigación científica, que realizan maestro y alumnos de las diferentes sedes académicas, para así contribuir mas a la investigación y que de igual manera sea un complemento de estudio para la Licenciatura en Educación para la Salud y para la Maestría en Sociología de la SaludEl libro contiene diversas temáticas que muestran conocimientos, metodologías, técnicas, herramientas y lenguajes necesarios utilizados comúnmente en el área de las Ciencias Sociales y de la Salud, desde un enfoque multi y transdisciplinario para poder indagar los elementos que componen la diversidad, la multiculturalidad y el medio ambiente que gira en torno a los temas de salud y de los estilos de vida saludabl

EDUCACIÓN AMBIENTAL Y SOCIEDAD. SABERES LOCALES PARA EL DESARROLLO Y LA SUSTENTABILIDAD

Este texto contribuye al análisis científico de varias áreas del conocimiento como la filosofía social, la patología, la educación para el cuidado del medio ambiente y la sustentabilidad que inciden en diversas unidades de aprendizaje de la Licenciatura en Educación para la Salud y de la Maestría en Sociología de la SaludLas comunidades indígenas de la sierra norte de Oaxaca México, habitan un territorio extenso de biodiversidad. Sin que sea una área protegida y sustentable, la propia naturaleza de la región ofrece a sus visitantes la riqueza de la vegetación caracterizada por sus especies endémicas que componen un paisaje de suma belleza

Correction: Loredo Varela, R.C.; Fail, J. Host Plant Association and Distribution of the Onion Thrips, <i>Thrips tabaci</i> Cryptic Species Complex. <i>Insects</i> 2022, <i>13</i>, 298

In the original publication [...

Host Plant Association and Distribution of the Onion Thrips, Thrips tabaci Cryptic Species Complex

Onion thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera: Thripidae) is a pest of economic importance traditionally treated as a polyphagous, cosmopolitan single species. Recent genetic evidence, however, suggests that it is rather a cryptic species complex of three lineages referred to by their host association and displaying different biological and ecological characteristics: leek-associated 1, leek-associated 2 and tobacco-associated. This study reviews host plant associations and distribution of the lineages of this cryptic species complex and discusses its consequences from an agronomical perspective. Overall, leek-associated 2 lineage has the broadest host range, including major crops from different plant families, and it is the only lineage with a confirmed worldwide distribution. Leek-associated 1 lineage shares some host plants with leek-associated 2. It is often found in Allium crops and its geographic distribution is limited to a few dozen countries. Finally, tobacco-associated lineage has only been collected from tobacco and their associated weeds in central and east Europe, and the Middle East. Additionally, this work presents a list of 391 plant species on which breeding and development of T. tabaci occurs, regardless of lineage. These host plant species belong to 64 different families, most importantly Asteraceae, Fabaceae, Brassicaceae, Poaceae, and Solanaceae

Antigp41 membrane proximal external region antibodies and the art of using the membrane for neutralization.

International audienceWe summarize the latest research on the progress to understand the neutralizing epitopes present within the membrane proximal external region (MPER) of the HIV-1 fusion protein subunit gp41.The HIV-1 fusion protein subunit gp41 contains a highly conserved sequence that is essential for membrane fusion and targeted by broadly neutralizing antibodies such as 2F5, 4E10, Z13e1, and 10E8. These antibodies recognize a linear gp41 epitope with high affinity, but require additional hydrophobic sequences present in their heavy chain CDR3 for neutralization. Recent structural studies on mAbs 4E10 and 10E8 provide molecular details for specific interactions with lipids and implicate part of the transmembrane region as the relevant 10E8 epitope. Although many different approaches have been applied to engineer gp41 immunogens that can induce broadly neutralizing antibodies directed toward MPER, only modest success has yet been reported.The new structural details on the complex gp41-lipidic epitope will spur new approaches to design gp41-MPER immunogens that might induce broadly neutralizing antibody responses